U.S. Pat. No. 3,275,295 granted on Sep. 27, 1966 to J. M. Allen and A. J. Scalzo entitled "Elastic Fluid Apparatus" discloses a box-like element on the inner diameter of the stator vane that when assembled define an annular vane construction for a gas turbine engine. The inner shroud or base portions carries interlocking means for interlocking adjacent vanes. The fit of the interlocking means is such that it provides damping. A band formed from relatively thin strip rigidly connects to each of the base members to hold them in frictional engagement relative to each other while permitting radial expansion. The method of bonding the thin strip to the base member is by welding which would require that each of the members are metallic.
As is well known in the aeronautical art, it is highly desirable to reduce the weight of engine component parts inasmuch as such a reduction translates into fuel savings and/or greater payload capacity. One area that has proven to lend itself to being fabricated from composite materials is the fan/compressor section of the engine. Since this area during aircraft operations can become relatively warm and encounter extremely high stresses, only certain composite materials have proven to be satisfactory for this environment. One of the materials that have proven to exhibit satisfactory characteristics is the imide resin and carbon fiber family of composite materials. However, because of the characteristics of this material, fabrication of the vane has been particularly difficult.
I have found that a vane can be satisfactory fabricated by forming the vane in segments comprising the inner shroud, outer shroud and at least two and perhaps three airfoils extending between the inner shroud and outer shroud. The airfoils of the stator vane are fabricated into a solid body with an integral hollow box-like structure formed at the base of the vane to define the inner shroud. The box-like structure carries a pair of opposing side walls a bottom wall and top wall and the ends are void to define an annular cavity when the segments are assembled in a ring like stator vane. One end of the hollow box-like element is necked down to fit into the end of the adjacent segment. This construction forms an extremely light weight assembly and doesn't require any additional structural supports as is the case of heretofore known assemblies.
Also, circumferential tracks formed from a suitable abradable material is permanently affixed to the inner diameter of the inner shroud and when assembled mates with the knife edge sealing elements of the labyrinth seal carried by the rotating shaft.